There is a continuing need for lightweight containers that have a high longitudinal and lateral strength. A high longitudinal and lateral strength container resists both bulging and paneling. Paneling is when some of the head space gases are absorbed by the contents of the bottle to create a slight vacuum. This can cause the front or rear wall to buckle inwardly. A container will bulge when the wall strength is less than the force exerted on the container walls by a contained substance or from container stacking. Both of these effects are problems. Each changes the original shape of the container.
There also is a need for lightweight, high strength containers at the manufacturing and distribution levels. The containers must be sufficiently strong to withstand the forces during filling and handling, and then later during distribution when packing cases and/or the containers will be stacked, one on the other. Also there must be a sufficient strength when handled by the consumer during use. The container must retain its integrity so that there will be no spills or other such events.
There is a continuing need for containers that have a lighter weight. This results in a lower cost and less material to recycle once the container is emptied of its contents. The problem is how to make a lightweight container that will substantially retain its shape during usage, that is, how to make a bottle that has a high lateral and longitudinal strength. These are competing objectives.
This problem is partially addressed by the Perwoll product bottle. This is a German product. In this bottle there are front and rear walls and connecting sidewalls. There also are flat sections between each of these walls. This bottle partially solves the problem. However, in order to get lightweight container and high longitudinal and lateral strength between the front wall and the sidewalls, and between the rear wall and the sidewalls, there should be concave transition walls. A concave shape to a transition wall increases the strength of the container both laterally and longitudinally. In addition, it has been found that the handle area can likewise be strengthened if between the wall of the handle area and the front, rear and sidewalls, there also is a concave transition wall. That is, in any transition from one container wall to another container wall there should be a concave transition wall. A transition wall with a concave structure permits the use of less container material but yet retains the overall container strength.